Some engines do this, an easy fix is to put intake venturis on the carbs You can get plastic ones for only a few dollars, aluminum ones cost more, or you can make your own. The venturis catch the spitting and then the next intake pulse sucks it back in. Fuel mileage goes up cause you are not wasting fuel, and the plane stays cleaner because the fuel is not blown all over. I guess the venture helps tune the intake pulse, but I am not sure how much if any performance is raised.

Sincerely, Richard/Club SAITO #635
"Always On, Slightly Off"